Pure Tungsten Diverter Module Made of Additive Materials

Additional material manufacturing is a new processing technology, which is different from the traditional "removal" manufacturing. It does not need the original embryo and die. According to the computer three-dimensional model data of parts directly, it can form any complex shape object by adding material layer by layer. Nowadays, people have given the added material manufacturing a fashionable name - 3D printing.

Pure tungsten is a refractory metal with high melting point, high density, high temperature strength and high hardness. It is widely used in aerospace, national defense weapons, fusion energy and other fields. However, due to the high melting point and thermal conductivity of tungsten, the spreading/solidification behavior of molten droplets under the action of heat source is complex, and it is difficult to achieve complete densification. Therefore, the process and method of adding materials to pure tungsten have not been broken through.

No matter how difficult it is, researchers'creative thinking can not be stopped. With the passage of time, various unique pure tungsten augmentation manufacturing schemes have emerged. For example, some scholars have proposed a 3D printing method for pure tungsten metal augmentation manufacturing. The scheme is based on selective Laser Melting (SLM) or powder bed laser melting. Special pretreatment methods and process measures are adopted to ensure pure tungsten gold. The dense moulding technology of the genus is novel and has great potential. For example, using 3D printing pure tungsten technology to manufacture pure tungsten diverter module validation of artificial solar ITER Tokamak device:

1) Screening and proportioning of tungsten powder particles
The spherical pure tungsten powder particles without impurities and oxygen adsorption on the surface were selected, and the large tungsten powder particles and small tungsten powder particles were selected. The median particle size of large tungsten powder particles was 18.3 micron, the median particle size of small tungsten powder particles was 2.1 micron, and the particle size ratio of small tungsten powder particles to large tungsten powder particles was 0.11. The small tungsten powder particles were mixed with large tungsten powder particles at 3:7, and the mixed powder was obtained. La and carbon black were added into the powder, and the quality of La was 0.3% of that of mixed powder and 0.3% of that of carbon black.

2)Laser Forming and Remelting

A.Install the multi-layer composite iron-insulating material-tungsten substrate on the working platform, preheat to 300 C and maintain this temperature during laser forming and remelting. The gap between the POWDER-LAYING scraper and the multi-layer composite iron-insulating material-tungsten substrate is 30 um. In the glove box protected by argon, fill 1) the prepared mixed powder into the powder bin.

B.Sealed forming chamber, pumping vacuum to the relative vacuum of - 90KPa, injecting protective gas argon into the forming chamber; repeatedly pumping vacuum and importing protective gas argon, so that oxygen content in the forming chamber can be reduced to less than 300 ppm.

C.Scanning the "sacrificial area 4" of the multi-layer composite "steel-insulating material-tungsten" substrate by laser, consuming the residual oxygen in the forming chamber until the oxygen content drops below 50 ppm.

D.The powder laying mechanism feeds the mixed powder in the powder silo onto the multi-layer composite "steel-insulating material-tungsten" substrate, and is paved by the powder laying scraper to obtain a thin layer of mixed powder with a thickness of 30 microns.

E.Starting forming, the mixed powder of section area 1 was melted by high-energy laser beam. Within 30 minutes, the oxygen content in the forming chamber was reduced to less than 1 ppm, and the oxygen content in the forming chamber was always less than 1 ppm during the laser forming and remelting process. Laser power was more than 400 W, the point distance was 50 microns, the exposure time was 280 microns, and the scanning distance was 110 microns.

F.Laser scanning remelting without mixing powder. The angle between the scanning direction of laser remelting and the scanning direction of forming is 90 degrees, and the parameters are the same as those of E.

G.After remelting, the working platform drops one slice thickness by 30 microns.

H. Repeat step E-G until the whole part has been formed, and get the verification of pure tungsten diverter module of Tokamak device.

By optimizing the proportion of spherical tungsten powder and ensuring the forming process, the problems of unstable droplet state, spheroidization and more defective holes in pure tungsten metal additives manufacturing are solved, and the forming density and component performance are improved. Compared with the traditional tungsten alloy sintering method, the adding material manufacturing can save a lot of time and cost.

• < Prev
• Next >